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+<?php
+/**
+ * Elgg Data import export functionality.
+ *
+ * @package Elgg.Core
+ * @subpackage DataModel.Export
+ */
+
+/**
+ * Get a UUID from a given object.
+ *
+ * @param mixed $object The object either an ElggEntity, ElggRelationship or ElggExtender
+ *
+ * @return the UUID or false
+ */
+function get_uuid_from_object($object) {
+ if ($object instanceof ElggEntity) {
+ return guid_to_uuid($object->guid);
+ } else if ($object instanceof ElggExtender) {
+ $type = $object->type;
+ if ($type == 'volatile') {
+ $uuid = guid_to_uuid($object->entity_guid) . $type . "/{$object->name}/";
+ } else {
+ $uuid = guid_to_uuid($object->entity_guid) . $type . "/{$object->id}/";
+ }
+
+ return $uuid;
+ } else if ($object instanceof ElggRelationship) {
+ return guid_to_uuid($object->guid_one) . "relationship/{$object->id}/";
+ }
+
+ return false;
+}
+
+/**
+ * Generate a UUID from a given GUID.
+ *
+ * @param int $guid The GUID of an object.
+ *
+ * @return string
+ */
+function guid_to_uuid($guid) {
+ global $CONFIG;
+
+ return elgg_get_site_url() . "export/opendd/$guid/";
+}
+
+/**
+ * Test to see if a given uuid is for this domain, returning true if so.
+ *
+ * @param string $uuid A unique ID
+ *
+ * @return bool
+ */
+function is_uuid_this_domain($uuid) {
+ global $CONFIG;
+
+ if (strpos($uuid, elgg_get_site_url()) === 0) {
+ return true;
+ }
+
+ return false;
+}
+
+/**
+ * This function attempts to retrieve a previously imported entity via its UUID.
+ *
+ * @param string $uuid A unique ID
+ *
+ * @return mixed
+ */
+function get_entity_from_uuid($uuid) {
+ $uuid = sanitise_string($uuid);
+
+ $options = array('metadata_name' => 'import_uuid', 'metadata_value' => $uuid);
+ $entities = elgg_get_entities_from_metadata($options);
+
+ if ($entities) {
+ return $entities[0];
+ }
+
+ return false;
+}
+
+/**
+ * Tag a previously created guid with the uuid it was imported on.
+ *
+ * @param int $guid A GUID
+ * @param string $uuid A Unique ID
+ *
+ * @return bool
+ */
+function add_uuid_to_guid($guid, $uuid) {
+ $guid = (int)$guid;
+ $uuid = sanitise_string($uuid);
+
+ $result = create_metadata($guid, "import_uuid", $uuid);
+ return (bool)$result;
+}
+
+
+$IMPORTED_DATA = array();
+$IMPORTED_OBJECT_COUNTER = 0;
+
+/**
+ * This function processes an element, passing elements to the plugin stack to see if someone will
+ * process it.
+ *
+ * If nobody processes the top level element, the sub level elements are processed.
+ *
+ * @param ODD $odd The odd element to process
+ *
+ * @return bool
+ * @access private
+ */
+function _process_element(ODD $odd) {
+ global $IMPORTED_DATA, $IMPORTED_OBJECT_COUNTER;
+
+ // See if anyone handles this element, return true if it is.
+ if ($odd) {
+ $handled = elgg_trigger_plugin_hook("import", "all", array("element" => $odd), $to_be_serialised);
+ }
+
+ // If not, then see if any of its sub elements are handled
+ if ($handled) {
+ // Increment validation counter
+ $IMPORTED_OBJECT_COUNTER ++;
+ // Return the constructed object
+ $IMPORTED_DATA[] = $handled;
+
+ return true;
+ }
+
+ return false;
+}
+
+/**
+ * Exports an entity as an array
+ *
+ * @param int $guid Entity GUID
+ *
+ * @return array
+ * @throws ExportException
+ * @access private
+ */
+function exportAsArray($guid) {
+ $guid = (int)$guid;
+
+ // Trigger a hook to
+ $to_be_serialised = elgg_trigger_plugin_hook("export", "all", array("guid" => $guid), array());
+
+ // Sanity check
+ if ((!is_array($to_be_serialised)) || (count($to_be_serialised) == 0)) {
+ throw new ExportException(elgg_echo('ExportException:NoSuchEntity', array($guid)));
+ }
+
+ return $to_be_serialised;
+}
+
+/**
+ * Export a GUID.
+ *
+ * This function exports a GUID and all information related to it in an XML format.
+ *
+ * This function makes use of the "serialise" plugin hook, which is passed an array to which plugins
+ * should add data to be serialised to.
+ *
+ * @param int $guid The GUID.
+ *
+ * @return xml
+ * @see ElggEntity for an example of its usage.
+ * @access private
+ */
+function export($guid) {
+ $odd = new ODDDocument(exportAsArray($guid));
+
+ return ODD_Export($odd);
+}
+
+/**
+ * Import an XML serialisation of an object.
+ * This will make a best attempt at importing a given xml doc.
+ *
+ * @param string $xml XML string
+ *
+ * @return bool
+ * @throws Exception if there was a problem importing the data.
+ * @access private
+ */
+function import($xml) {
+ global $IMPORTED_DATA, $IMPORTED_OBJECT_COUNTER;
+
+ $IMPORTED_DATA = array();
+ $IMPORTED_OBJECT_COUNTER = 0;
+
+ $document = ODD_Import($xml);
+ if (!$document) {
+ throw new ImportException(elgg_echo('ImportException:NoODDElements'));
+ }
+
+ foreach ($document as $element) {
+ _process_element($element);
+ }
+
+ if ($IMPORTED_OBJECT_COUNTER != count($IMPORTED_DATA)) {
+ throw new ImportException(elgg_echo('ImportException:NotAllImported'));
+ }
+
+ return true;
+}
+
+
+/**
+ * Register the OpenDD import action
+ *
+ * @return void
+ * @access private
+ */
+function export_init() {
+ global $CONFIG;
+
+ elgg_register_action("import/opendd");
+}
+
+// Register a startup event
+elgg_register_event_handler('init', 'system', 'export_init', 100);